1. Field of the Invention
In one aspect this invention relates to leading trailing drum brakes. In a further aspect, this invention relates to self-adjusting mechanisms useful with leading trailing brakes.
2. Prior Art
Leading trailing brake structures with manual adjustment means are well known in the art and have been used in vehicle applications for many years. The art has gradually evolved a variety of self-adjusting mechanisms where, when the brake shoes are separated from the associated drum by a distance greater than a predetermined minimum, a pawl or other activation means will turn a ratchet wheel which lengthens the strut, thereby increasing the separation between the shoes and adjusting the distance the brake shoes must travel in order to engage the brake. Such self-adjustment mechanisms were an improvement in that the brake was constantly being adjusted and the car need not be removed from service in order to adjust the brakes to the proper spacing. However, such adjusters had certain problems. Normally the strut had at least one end which was a forked or bifurcated portion engaging the web in one of the brake shoes. If the brake shoe separation became excessive due to unusual braking forces of the application of the mechanical parking brake, simultaneously with service brake activation, it was possible for this strut to become disengaged from the brake shoe resulting in the loss of rear braking. Also, the prior art brakes normally had called for adjustment mechanisms which comprised several parts in which they were rotatably mounted to the brake's web by means of various pins and shafts. Such structures were difficult to assemble and resulted in increased assembly problems and cost.